You'll need:
1. Powder measure to measure the powder charge.
2. Flask to dispense powder into the measure, so not to dispense from the powder can.
3. Capper to help apply caps without using your fingers.
4. Nipple wrench to be able to remove the nipple for cleaning it.
5. Short starter to help get the patched round ball started down the muzzle.
6. Rod accessories:
a. cleaning jag to help grip a cleaning patch for wiping & cleaning.
b. patch worm or patch puller to grab and pull stuck patches out of the bottom of the barrel, (without needing to remove the breechplug).
c. fouling scraper sometimes comes in handy to clean the barrel breech, not really necessary if your rifle has a removable breechplug for cleaning.
d. cleaning brush for your caliber for removing stubborn deposits.
7. Nipple pick to clear the nipple of debris.
8. Bore Butter or Wonderlube to lubricate patches for loading, and the barrel after cleaning and to help prevent rust.
9. Patches, .015 thickness, pre-lubed or saturate them with Bore Butter yourself.
10. Balls, .490 diameter
11. Powder
12. #11 Percussion caps
13. BP cleaning solvent - will help to clean the gun without using water, and is very helpful if using Pyrodex.
14. Powder
15. BP Cleaning rod or kit, it's longer and has a handle for easier cleaning without using the short ramrod.
16. Ramrod - I recommend buying a wooden dowel nearly as thick as the bore caliber at a hardware store for about $1. Drill a hole in a ball, a hunk of plastic or piece of wood to make a handle for it and this will help to make ramming the bullet or ball down the barrel much easier by giving better leverage. Mine are 7/16 th's in diameter and have never broke.
For a .50 caliber percussion gun, usually the common starting point for working up an accurate load is to use the .490 balls and a lubricated patch with a thickness of .015.
There are other diameter balls like .495, and other patch thicknesses, like .005 (too thin), .010, .018 (blue stripe pillow ticking), .020 (maybe too thick).
The recommended starting powder load is the same number as the caliber of the barrel, 50 grains by volume.
If buying .495 balls, start with a .010 patch or loading may be difficult.
Did you ever imagine that this could get so expensive?